Utilization of waste gases



Patented AJim 2s, 193s U'rnJzA'rIoN oFl WASTE GASES Adolph W. Lissauer, Louis'ville, Ky., assigner to Louisvill e Drying Machinery lCompany, In-

corporated, Louisville, Ky., a 'corporation of Kentucky Application July 27, 193s, senal 10.22.832

4 Claims.

'I'his invention relates generally to the utilization of hot waste gases in the drying of various materials. Although the teaching of the same may be followed regardless of the origin of the Y 5 gases, as an illustration the invention is disclosed in connection with the operation of the conventional distillery. It is to be expressly understood. however, that the invention is limited in nov way to this particular application, but on the contrary may be used in connection with gases derived from any source.A

In the usual practice, large volumes of waste gas from a distillery boiler plant are rejected at a temperature of about 500600 F. If the comis made of the gas in boilers, stills and the like,

the temperature of the same has been found to be insufficient for any adequate drying purpose despite the fact that it still contains valuq'uire drying gases of high temperature. At the same time that these valuable gases are wasted, it is the practice to generate all of the drying gasesv of high temperature from another source in order to dry the grain elements recovered from the distillery slop. Due primarily to the fact that emcient hot air driers require a drying medium at approximately 1100 F. no commercially successful use of cooler waste gases in such drlers, therefore, has even been made, so far as is known. n

It has now been found that if a relatively small volume of gas at a. temperature greatly in excess of that required for drying is mixed with Vthe waste gases,- the temperature of the mixed gases can be raised to a pointv where the waste gas may be used foreflicient drying. This is due prima- .i rily to the fact thatvthe Waste gas beingvat 500 F. or higher possesses an original increment of heat which materially lessens the Aheat transfer p45. load required'to bring the drying medium -up to Whileall the'v'11( )0 F. drying temperature.

. values of4 temperature `given herein are merely n yillustrative and are not to be .'onsidered as'limiting the scope of the invention, it is foundthat a small and eilicient auxiliary combustion Ameans can readily. generate suiiicient gas at 2600 F. which when mixed in relatively small .quantities lwith theglarger .volumeksof .the waste gas at SOO-600. F. will give-@an ample quantity of dryo5 ingmedium at 1100F.

bustion process is efiicient and a maximum use By employing an eiiicient combustion process for the auxiliary gas and a suitable control of the drying process, an increased evaporation effect per pound of fuel burned in the entire plant thus results. At the same time vthe costs of plant 5 installation are materially lowered since the combustion means for the relatively smallamount of auxiliary gas is much less expensive than the means heretofore used when all of the drying medium was separately generated. '10

The invention, therefore, has as a chief object the teaching of a method for utilizing the heat of waste gases.

A second object is the provision of an improved drying process which is less expensive to operate l5 and which requiresa minimum of equipment.

A third object is the provision of a drying process readily controlled in dependence upon critical temperatures of the drying medium.

Another object is the provision oi' an improvedv 20 control apparatus for driers.

Another object is the teaching of a method for incorporating the drying of by-products of an industrial plant into the normal operation of such plant.

y Other objects and advantages of the invention will become more apparent as the description y proceeds when considered in lconnection with the accompanying drawing in which` y y vFigure -1 is a view partially in section showing 30 yone form of apparatusvwhich may be usedtov carry out the invention and n. Figure 2 is a schematic view showing one modil ilcation .of the control means'wherein .allof the waste .gases pass through. the drying apparatus.. 35

As Awill be apparent to those skille'dlin the art, many. modifications` in the forms of drying apparatus, lcontrolmeans vand-heat generating equipment -mayrbe employed without departing from 4 the essentials of the invention `and,therefore'.40 :the invention is` not to be considered'as limited toy the exact. arrangement and apparatus shown `Referring now tov `FigureLa rotary drier Iv of any suitable c. construction, which'- for f example I 45 may bel of the ,-typedisclosedin United States Letters Patent, ,1,853,691v toA. W. -Lissauer et al.,

,isv mounted upon any `suitable supporting means and rotated by a suitable `actuating-"means. At `.loneQcgznydthedrier extends througha` chamber 50 ,2gfiilled .witha heating medium derivedv from sources disclosed hereinafter and having a suiilcient temperature iand volume to insure ani eilicientl drying of the wet material introduced into said drier by, a., conveyor 3. This conveyor is driven from a suitable regulated source of power by member 4 and moves into the drier'the material introduced into hopper 5 along with such air as may enter with the material into the hopper.

Extending into the closed inlet end of the drier is an exhaust conduit 6 for the purpose of receiving the exhaust gases and the moisture resulting from the drying process. This exhaust conduit leads through a casing 1 in which is housed a suitable exhaust fan (not shown) and connects with a second conduit 8 leading into a cyclone separator or other suitable apparatus 9 from which the exhaust gases and moisture may escape and in which any small particles of dried material entrained by such gases may be recovered.

At itsoutlet end drier I is provided with a suitable casing lor manifold I0 having a lower restricted spout member II from which dried ma- -terial falling from the open end of the drier interior may be taken. On its interior drier l may be provided with suitable conduits I2 having openings I3 communicating with chamber 2 and terminating in an open end within the casing I0. The heating medium thus exerts a drying effect upon the material in the drier by radiation from and by conduction of heat through conduits I2. Upon leaving conduits I2 the heating medium passes countercurrent to the movement of material and isable to continue its drying effect by direct contact with such material.

Atv20 vis indicated generally the exhaust stack of an industrial boiler plant from which all of the waste gases may be led through a conduit 2| into chamber 2 when the drying process is to. be carried out. These waste gases will usuallyvhave atemperature ranging from 50G-600 F. whichis insuiicient'to dry the material both thoroughly and efficiently. In order, therefore, .to increase the temperature of the heating medium entering the drier, anl auxiliary combustion means 22 of any suitable nature, such for example as a furnace equipped with a stoker driven by a'suitable electric motor 23,' may be employed.

As an aid to theregulation of temperature and volume of the heating medium incident to theA drying at different loads, a bypass 24 controlled by a regulating means 25 is interposed between conduits .6 and 2|.

For purposes of regulating the drying process any suitable. means may beemployed to vary thel temperature of the heating medium entering the drier and/or the temperature of theexhaust medium leaving thel drier. One such means is shown in Figure 1 wherein a compressed air liner 30 leads to a diaphragm actuated means 3| con'- f nected to regulating means 25 and controlled .by l a conventional thermostat32 in dependence upon. the temperature of the exhaust medium in ex-f haust conduit 6.

A second compressed air line 33 leads toa sec-.e111 'ond diaphragm actuatedmeans 34 connected lto the controls of motor23 and arranged to `change the speed of such motorA and to vary the -feed of the stoker driven thereby, whereby thefgeneration of auxiliary gases by furnace 22 may be regulated.

A conventional thermostat 35 located within.; chamber 2 adjacent the point where the hot mixed" gases enter the drier conduits I2 vcontrols the` action of diaphragm means 34 in dependence upon the temperature of the heating medium entering...

the drier.

By means of the arrangement thus described'- the following method of utilizing the waste gases and controlling the drying process results. 1n-

'.,atfall'yIv times.

this f I 35 :located in; f chamber l2 stead of conducting the drying process as a separate adjunct to the operation of the main plant the same now becomes a unitary part of the plant operation. Gases generated in the main plant after having served their initial function are directed wholly through conduit 2| into chamber 2 with a temperature of 50G-600 F. In the usual case whenwdrying a product such as grains recovered from distillery slop, the temperature of the drying medium entering the drier should be approximately 1100 F. to insure adequate drying of the grain and the temperature of the exhaust medium leaving the drier should be approximately 250 F. when the grain is adequately dried. Assuming that thermostats 32 and 35 are so calibrated, the initial waste gases are too low in temperature Vto dry.-the material. Thermostat 35 then permits diaphragm 34 to operate to increase the generation of auxiliary gases at a temperature about 2600 F2 from furnace 22 in order to bring the mixed heating medium up to 1100 F.

At the same time, if the gas entering the drier is not of suiiicient temperature to dry the material, the temperature of the exhaust medium leaving the drier tends to fall below 250 F. indicating that the material li's not dried suiiciently and thermostat 32 acts through diaphragm 3| to open by pass control means 25 and reduce the proportion of low temperature waste gases passing of burning the material, thermostat' 35 becomes effective to diminish the generation of the auxil' iary gases. Furthermore, if the temperature of the exhaust gas exceeds l250 F., indicating that the material is being dried too much, thermostat 32 b omes effective to-operate diaphragm 3| and to close the by pass controlmeans, thus increasing .A

the proportion of they low temperature. wastegas and thus lowering the temperature of the mixed heating medium. Since the temperatures of the exhaust gasv from the drier is dependent upon the temperature of the heating mediumA entering the drier and upon the factors of gas volume, nature of material to be dried and quantity of material to be dried, it follows that a proper design ofthe drier and a proper calibration of the ycontrol I means described will result in an efficient andv satisfactory'drying operation.

Various Amodiiications of controllingthe operationfvjwhile utilizing the.` waste gases of the boiler` stack, v2li f will Suggest themselves-'Ltd .one

and all of the 'waste 'i `speed of motor 123 througlifdiaphragm means |34 omitterclj4 skilledintheart withcutonstitutipgadeparture from-.the invention." One such modification/is' f shownin `:Figure2,1'wlie medium iallsb'elow 110,0?"F, may bedone-by constructingthe cox'iventic'inal"` thermostat controly fso that compressed air pressurevfrompipe, |33 increases thevv P1.esslnfe.` j0u l diaphragm when ,theftemperature 'off the gas finvch'amber 2y is 1 ontne lamentan" calibrated tov4 close at 250 amaca? u means supplying material to the drier and means pressed air pressure upon diaphragm means |34 through the pipe connections I" and to decrease the speed of motor 23 when the exhaust temperature increases above 250 F., which condition indicatesthat the 1100 F. heating medium is too hot for the load of material then being dried.

Havingthus described the invention. it will be apparent that many variations in design `and construction of the same may be employed without departing from the essentials thereof. With the intention, therefore, of including such changes in the .above disclosure of the invention. I claim- 1. The methodof utilizing waste'gas'es of originally insuiiicient temperature for drying a material comprising, generating auxiliary gases of K more than suillcient temperature to dry the material, mixing the waste gases with the auxiliary gases to bring the temperature of the mixture up to the requisite temperature for drying, drying the material by vcontact with the mixed gases mov` ing in a single pass through the drying process,

controlling the relative proportions of waste and auxiliary gases in dependence upon both the temperature of mixed gases prior to drying the inaterial and the temperature of the exhaust gases after drying the material and continuously exhausting the entire volume oi mixed gases from the drying process in order to avoid a high back pressure upon thelsource of waste gases. 2. Meansfor utilizing the waste gas of an industrial plant for drying material comprising, a drier assembly including a drier having ka continuously open path` for the exhaust ofthe drying gas, means directing the entire output of waste gas into the assembly, a by-pass in the assembly adapted to divert a part of the waste gas from passage through said drier, regulating means in the by-pass actuated in dependence upon the temperature of gases at the exhaust of the drier and adapted to control the volume of waste gas diverted .through the by-pass, means supplying auxiliary drying gas of higher temperature'thanthe waste gas to said drierfor mixing with undiverted waste gas for joint passage through said drier, control -means for the supply of said auxiliary gas actuated in dependence uponl the temperature or the mixed gases entering the drier,

directing'- the mixed gases to exhaust through the drier 'in a single pass in contact with the material in order to dry the material and to prevent a high back-pressure upon the waste gas loutlet -from the plant. l

3. Means for utilizing the waste gas of an industrial plant for drying material comprising, a drier assembly including a drier havingla continuously'openfpath for the exhaust kvof the dry- -ing gas, means-'directing the entire output oi waste gas into .the assembly, a by-pass inthe assembly'adapted to divert a part ofthe waste 'gas from passage through the drier, regulating means in said Aby-pass lactuated in dependence upon the temperature of gases at the exhaust of the drier and adapted to regulate the volume of waste gas ,enteringl the drier from the drier assembly, means supplyingauxiliary gas ofv higher temperature than said waste gas to said'drier for vmixing with the undiverted' waste gas for Joint passage through said drier, means supplying material to. the drier and means directing the mixed gases vto exhaust through said drier in a single pass in contact with the material in order to dry the material and to prevent a high back-pressure 'upon the -waste lgas outlet from the plant.

drier in dependence upon the temperature of the mixedgases entering vthe drier, means supplying wet material to said drier and means directing the mixed gases to exhaust through the drier in a single pass in contact with the material in order to dry the material and to -prevent a high back pressure upon the waste gas outlet from Ithe plant.

, ADOLPH W.- IJSSAUER. 

